A consistent problem which exists in the operation of a combine type harvester is that of rocks and other solid debris being picked up by the header of a combine from the ground surface, together with the cut crop, are carried into the feeder housing which in turn carries the crop up to the threshing mechanism of the harvester. Such debris, depending on its size and shape, may cause damage to the conveyors which transfer the cut crop from the header to the feeder housing of the combine, particularly where such conveyors are of the auger type, as well as affecting the conveyor in the feeder housing. However, severe damage usually occurs if a rock, for example enters the threshing area, which commonly consists of a beater arrangement.
Accordingly, various forms of stone traps have been developed, for example as shown in early U.S. Pat. No. 3,971,390, Jul. 27, 1976 to McDuffie et al., which have usually been found relatively effective if located in the feeder housing provided for transferring the cut crop in the combine unit from the header to the threshing area. Other known designs have located a rock trap or sump at the entrance to the concave of the beater of the threshing mechanism, such as in U.S. Pat. No. 5,702,360, Dec. 30, 1997 to Wilson. Various means have been developed for automatic dumping of the rocks behind the header, such as mechanisms which actuate to drop the rocks depending on the weight occurring on the trap door. More recently, more elaborate detection apparatus, such as electronic detecting means have been developed for operation of a trap door. An example of such an arrangement is shown in U.S. Pat. No. 6,601,372, Aug. 5, 2003 to Helnsey.
Such systems have added significantly to the cost of a combine unit, but are nevertheless utilized because of the severity of the damage which a solid article entering the combine unit can cause. On the other hand, because of the conditions to which a combine is subjected, including dust, jamming of the crop, etc., damage which does occur to the more complex detection system itself as well to the mechanism which it operates can be costly. The consequences of their failure, continues to be a serious problem. As an alternative, more simple devices which are mounted on the header, rather than in association with feeder housing of the combine have been used. Such devices are commonly referred to as dams and are shown, for example, in U.S. Pat. No. 6,070,401, Jun. 6, 2000 to Johnson. Clearly, however, they are not practical for use with most types of crop harvesting in that they interference with the normal delivery of the cut crop from the sickle bar.